I can't remember if there is a reason why it's checking so often, or if that's just something done by windows behind the scene -- but basically it's a check to make sure the performance counters aren't disabled -- since these counters are what enables PT to check cpu usage.

So bottom line -- it's proper that PT is checking this registry value, but i'm not sure why it's happening so often, and i'll go back into the code and see if its a bug or if there is a good reason for it and post about my findings.